Field of the Invention
The invention relates generally to power subsystems for downhole equipment such as electrical submersible pumps (ESP's), and more particularly to means for maintaining a desired amount of compressive force applied to an elastomeric seal.
Related Art
Downhole equipment such as ESP systems are commonly installed in wells for purposes of producing fluids (e.g., oil) from the wells. Power suitable to drive the equipment is produced at the surface of the wells and is delivered to the equipment via power cables that extend into the wells. The power cables are typically connected to the downhole equipment via “pothead” connectors that couple the power cable to the downhole equipment.
The environment downhole in a well may be very harsh. For instance, the temperature may be several hundred degrees, the fluids in the well may be corrosive, and particles in the fluids may be abrasive. These conditions can cause the components of an ESP system to degrade and possibly fail, thereby shortening the useful life of the ESP system.
High temperatures downhole are increasingly problematic. The temperature of the geological formation in which a well has been drilled is often high (e.g., 300 degrees F.) even in the absence of the downhole equipment. When an ESP system is operated downhole, it generates additional heat that increases the temperature around the system. The problem of high environmental temperatures is made even worse when techniques such as SAGD (steam assist, gravity drain) are employed to heat oil in the formation to reduce its viscosity and facilitating pumping.
The well environment may affect the power cabling and associated electrical junctions, as well as the ESP itself. For instance, temperature changes may cause the elastomeric materials that are used to form seals in the electrical junctions to expand and contract at rates which significantly differ from those of other materials used in the junctions. This may in turn cause the contact pressure of the seals against other components to vary from the ranges for which they were designed, which may result in leakage around the seals and consequent degradation and failure of the seals.
It would be desirable to provide improved means for providing seals in electrical junctions that reduce the effects of high temperatures and temperature changes in well environments on the seals are reduced.